Protective gas generating heating system for asphalt tanks

ABSTRACT

A protective gas generating heating system for asphalt tanks comprising an oil or gas fired heating tube in a closed, asphalt tank, the heating tube generating predominately carbon dioxide and water vapor as an exhaust gas, an exhaust stack connected at one end to the heating tube and at the opposite end to the inlet of a condensing and cooling coil, a compressor connected at its lower pressure inlet to the outlet of the cooling and condensing coil and at its higher pressure outlet to an accumulator tank, a conduit connecting the accumulator tank to the top of the asphalt tank, and a pressure regulator in the conduit adapted to maintain a predetermined, minimum positive pressure in the asphalt tank.

United States Patent Martin [75] Inventor: Charles K. Martin, Boonton,NJ. [73] Assigneez Kimar Corporation, Keyport, NJ. [22] Filed: Aug. 23,1973 [21] Appl. No.: 391,044

[52] US. Cl. l26/343.5 A, 432/23 [51] Int. Cl. E0lc 19/45 [58] Field ofSearch 126/3435 A; 432/23 [56] References Cited UNITED STATES PATENTS2,124,764 7/1938 Comstock 432/23 X 2,275,106 3/1942 Hayes 432/23 X3,305,138 2/1967 Plumb 126/3435 A 3,348,739 10/1967 Brock 126/3435 A3,503,382 3/1970 Wollner 126/3435 A 3,749,082 7/1973 Brock 126/3435 APROTECTIVE GAS GENERATING HEATING SYSTEM FOR ASPHALT TANKS ASPHALT TANKPrimary Examiner-William F. ODea Assistant ExaminerPeter D. FergusonAttorney, Agent, or FirmPopper, Bain, Bobis, Gilfillan & Rhodes [57]ABSTRACT A protective gas generating heating system for asphalt tankscomprising an oil or gas fired heating tube in a closed, asphalt tank,the heating tube generating predominately carbon dioxide and water vaporas an exhaust gas, an exhaust stack connected at one end to the heatingtube and at the opposite end to the inlet of a condensing and coolingcoil, a compressor connected at its lower pressure inlet to the outletof the cooling and condensing coil and at its higher pressure outlet toan accumulator tank, a conduit connecting the accumulator tank to thetop of the asphalt tank, and a pressure regulator in the conduit adaptedto maintain a predetermined, minimum positive pressure in the asphalttank.

10 Claims, 1 Drawing Figure PRESSURE o TANK PROTECTIVE GAS GENERATINGHEATING SYSTEM FOR ASPHALT TANKS BACKGROUND OF THE INVENTION Asphalttanks must be heated in order to maintain the asphalt sufficiently fluidfor discharge through appropriate valves and conduits in the bottom ofthe tank. Asphalt, particularly heated asphalt possesses the inherentquality of forming a virtually solid surface skin at the interfacebetween the top surface of the asphalt and the atmosphere, generallyair, at the top of the asphalt tank.

The virtually solid skin on the top surface of the asphalt is notdissipated when fresh asphalt is added to the tank through its top.Thus, multiple layers of spaced apart, virtually solid skin are formedas the asphalt tank is refilled from the top, each skin layer descendingwith the withdrawal of asphalt from the bottom of the tank until itreaches the discharge valves and conduits. The skin thereupon occludesthe valves and conduits requiring the asphalt tank to be first emptiedof the asphalt above the skin layer and then cleaned.

Surface skins form over varying periods of time dependent upon the typeof asphalt involved. In the Roofing Industry, the asphalt has arelatively high melting point with the result that skin forms relativelyrapidly resulting in the necessity of cleaning the asphalt tank three tofour times per year. ln the Road Surfacing lndustry, the asphalt has asomewhat lower melting point with the result that skin forms somewhatless rapidly. However, even in the Road Asphalt Industry, tanks must becleaned approximately once a year.

Because the skin which forms from the contact of air and asphalt willnot remelt, raising the temperature of the tank is no avail. If anasphalt tank must be cleaned three or four times a year, present laborcosts involve the expenditure of from $3,000.00 to $4,000.00 togetherwith the loss of use of the tank during the down time.

Thus, there is great need for a system which will significantlyattenuate or prevent the formation of the relatively solid skin on thesurface of asphalt in the tank.

It has been found that atmospheres less reactive then oxygen with theasphalt tend to attenuate the formation of the skin. One such atmosphereis nitrogen. However, nitrogen is relatively expensive and thereforeeconomically undesirable. Additionally, rather expensive nitrogenhandling equipment must be employed to use the more economical liquidnitrogen as a source material such equipment involving a vaporizer whichpermits the liquid nitrogen temperature to rise sufficiently to preventfreezing of the upper surface of the asphalt.

Among the objects and advantages of the present invention is aprotective gas generating heating system for asphalt tanks whichgenerates not only the heat necessary to maintain fluidity of theasphalt but also an exhaust gas which is predominately carbon dioxideand water vapor, carbon dioxide being significantly less reactive withasphalt then air. The carbon dioxide exhaust gas from the heatgenerating means is withdrawn from the tank, compressed and stored in anaccumulator tank for return to the top of the tank bearing the asphaltwhere it is employed to purge the normally present residual airsubstituting a blanket of non-reactive carbon dioxide.

SUMMARY OF THE INVENTION A protective gas generating heating system forasphalt tanks comprising a tank, heat generating means in the tank; theheat generating means normally producing an exhaust gas capable ofsignificantly retarding the formation a highly viscose surface skin onthe asphalt normally generated by the action of air, an exhaust gasstack connected between the heat generating means and the exterior ofthe tank, gas compressor means having a low pressure inlet and a highpressure outlet, the low pressure inlet being connected to the exhaustgas stack, an exhaust gas accumulator tank connected to the highpressure outlet of the compressor means, and conduit means connectedbetween the accumulator tank and the interior of the first said tank.

PREFERRED EMBODIMENT OF THE INVENTION The objects and advantagesaforesaid as well as other objects and advantages may be achieved by theprotective gas generating heating system for asphalt tanks a preferredembodiment of which is illustrated in the drawings in which:

FIG. 1 is a schematic elevation view of the system.

Referring now to the drawings in detail, the protective gas generatingheating system for asphalt tanks comprises an asphalt tank 11 having agas or oil fired heating tube 12 mounted in the bottom thereof. Theheating tube 12 comprises a fuel delivery and ignitor assembly 13 and afire tube 14. The fire tube 14 heats asphalt 15 by means of directconduction from the wall thereof to the asphalt and through the asphaltby convection. The heating tube 12 is well known in the Industry and inand of itself needs no further elaboration.

An exhaust gas conduit 16 is connected to the end of the fire tube 14opposite the fuel delivery and ignitor assembly 13. The exhaust conduit16 extends generally parallel to the fire tube 14 and then upwardly as ataxhaust stack 17 which extends from the fire tube 14 to and through thetop 18 of the tank 11.

The exhaust stack 17 extends through an insulating jacket 19 which isclosed at its bottom 20 and which is open to the air at its top 21 whichextends above the top 18 of the tank 11.

The exhaust stack 17 is connected to an exhaust conduit 22 which is inturn connected to a condensing end cooling coil 23. The condensing andcooling coil may be either air or water cooled and is of a conventionaldesign.

The outlet end 24 of the condensing and cooling coil is connected to anautomatic condensate drain 25 which is in turn connected to the lowpressure inlet of a compressor 26. The high pressure outlet of compres-"sor 26 is connected through conduit 27 to a high presscribed, in theevent that the supply of exhaust gas in the accumulator tank 28 becomessufficiently depleted that it can no longer maintain an adequateblanketof exhaust gas in space 31 above the surface 32 of the asphalt15, a supplemental protective gas generating system 33 may be connectedthrough conduit 34 to conduit 29. The supplemental gas generating system33 may be another fossil fuel combustion burner system as described withrespect to the asphalt tank 11 or some other system capable ofgenerating a compatable protective gas. The protective gas generatingheating system for the asphalt tank is preferably operationallyconnected to controls for the auxiliary generating system 33 so that inthe event that there is inadequate pressure in accumulator tank 28, thesupplemental system 33 is automatically energized.

In operation, the protective gas generating heating system is energizedby energizing the fuel supply and ignitor assembly 13 which generatesflame within the fire tube 14. Since the system is heated by combustionof a fossil fuel, the exhaust gas is predominatly carbon dioxide andwater vapor with small quantities of carbon monoxide. The exhaust gaspasses through exhaust conduit 16 to the exhaust stack 17. The jacket 19prevents the formation of a skin on the stack 17 which would tend to begenerated by reason of its high temperature driving off the lowerboiling point constituents of the asphalt. Air circulating through theopen top of the jacket 19 cools the jacket to a sufficiently lowtemperature so as to prevent the formation of an asphalt skin thereon.

The exhaust gas passes from the stack 17 through conduit 22 to acondensing and cooling coil where water vapor condenses out and thetemperature of the exhaust gas is significantly lowered. Watercondensate is automatically drained through the automatic condensatedrain .25 and the water free cooled exhaust gas passes to the lowpressure inlet of compressor 26. Compressor 26 raises the pressure ofthe exhause gas and and passes it through conduit 27 to an accumulatortank 28.

Exhaust gas under positive pressure is automatically fed throughpressure regulator 30 to the interior of the tank 11 through conduit 29passing into the space 31 beneath the top 18 of the tank 11 and theupper surface 32 of the asphalt thereby purging air therefrom throughpurge valve 35. The predominately carbon dioxide exhaust gas preventsthe formation of the nearly solid skin on top of the asphalt 15.

Asphalt is normally added to an inlet valve 36 at the top of the tank 11and withdrawn through an outlet 37 in the bottom. Under proper operatingconditions, the level of asphalt 15 is never lowered to a level belowthe top of the fire tube 14 otherwise a skin would tend to form on thefire tube due to its high temperature. If the tank 11 is to be drainedthe fire tube 14 is preferably shut down so that its surface temperatureis not so high as to generate a skin as the level of the asphaltdescends beneath the level of the fire tube 14. Appropriate controls maybe provided to prevent the lowering of the asphalt.

The purge valve 35 is also preferably adapted to maintain at least aslight positive pressure in the tank 11 above the top 22 of the asphalt15 to prevent unintended air intrusion.

Under normal operating conditions, there is sufficient exhaust gasgenerated by the heating tube 12 to provide a protective air blanket inspace 31 at all times.

b. heat generating means in the tank, the heat generating means normallyproducing an exhaust gas capable of significantly retarding theformation of a highly viscous surface skin normally generated by theaction of air on asphalt,

c. an exhaust gas stack connected between the heat generating means andthe exterior of the tank,

(1. insulation means on the said stack within the said tank,

e. gas compressor means having a low pressure inlet and a high pressureoutlet, the low pressure inlet being connected to the exhaust gas stack,

f. an exhaust gas accumulator tank connected to the high pressure outletof the compressor means, and

g. conduit means connected between the accumulator tank and the interiorof the first said tank.

2. A protective gas generating system for asphalt tanks comprising,

a. the structure in accordance with claim 1 and b. water vaporcondensing means operatively connected between the stack and the gascompressor means.

3. A protective gas generating system for asphalt tanks comprising,

a. the structure in accordance with claim 1 and,

b. gas pressure regulator means operatively connected to the conduitmeans intermediate the said accumulator tank and the first said tank.

4. A protective gas generating system for asphalt tanks comprising,

a. the structure in accordance with claim 1 in which,

b. the heat generating means produces an exhaust gas which ispredominantly carbon dioxide. 5. A protective gas generating system forasphalt tanks comprising,

a. the structure in accordance with claim 1 in which,

b. the heat generating means burns a fossil fuel.

6. A protective gas generating system for asphalt tanks comprising,

a. the structure in accordance with claim 1 in which,

b. the heat generating means are positioned proximal to the bottom ofthe said tank. 7. A protective gas generating heating system for asphalttanks comprising,

a. the structure in accordance with claim 1 in which,

b. the said insulation means are a jacket through which the said stackextends. the jacket extending 6 from approximately the level of the saidheat gen- 0. the said heat generating means being positioned eratingmeans the top of the first said tank, proximal to the bottom of thefirst said tank and c. the jacket being closed at the bottom against theproducing an h t gas hi h is d minantl intrusion of asphalt and open tothe circulation of carbon dioxide air at the p f the h Said tank, thejacket being 5 10. A protective gas generating heating system for inspaced relationship to the stack. asphalt tanks comprising A protectlve3 generatmg heatmg system for a. the structure in accordance with claim9, in which phalt tanks comprising,

a. the structure in accordance with claim 1 m WhlCh, b. the Saidinsulation mean's are a jacket through 10 b. the heat generating meansproduces an exhaust gas whlch the Sa ld stack extends the Jacketextendmg which is predominantly Carbon dioxide from approximately thelevel of the said heat gen- 9. A protective gas generating heatingsystem for ash means to the top of the first sa1d tahk, h l tankscomprising, c. the acket being closed at the bottom against the a. thestructure in accordance with claim 1 and, ihtwsioh of asphalt and tf t0the eifeulatmh of b. gas pressure regulator means ti l air at the top ofthe first sa1d tank, the acket being nected to the conduit meansintermediate the said in spaced relationship to the stack. accumulatortank and the first said tank,

1. A protective gas generating heating system for asphalt tankscomprising, a. a tank, b. heat generating means in the tank, the heatgenerating means normally producing an exhaust gas capable ofsignificantly retarding the formation of a highly viscous surface skinnormally generated by the action of air on asphalt, c. an exhaust gasstack cOnnected between the heat generating means and the exterior ofthe tank, d. insulation means on the said stack within the said tank, e.gas compressor means having a low pressure inlet and a high pressureoutlet, the low pressure inlet being connected to the exhaust gas stack,f. an exhaust gas accumulator tank connected to the high pressure outletof the compressor means, and g. conduit means connected between theaccumulator tank and the interior of the first said tank.
 2. Aprotective gas generating system for asphalt tanks comprising, a. thestructure in accordance with claim 1 and b. water vapor condensing meansoperatively connected between the stack and the gas compressor means. 3.A protective gas generating system for asphalt tanks comprising, a. thestructure in accordance with claim 1 and, b. gas pressure regulatormeans operatively connected to the conduit means intermediate the saidaccumulator tank and the first said tank.
 4. A protective gas generatingsystem for asphalt tanks comprising, a. the structure in accordance withclaim 1 in which, b. the heat generating means produces an exhaust gaswhich is predominantly carbon dioxide.
 5. A protective gas generatingsystem for asphalt tanks comprising, a. the structure in accordance withclaim 1 in which, b. the heat generating means burns a fossil fuel.
 6. Aprotective gas generating system for asphalt tanks comprising, a. thestructure in accordance with claim 1 in which, b. the heat generatingmeans are positioned proximal to the bottom of the said tank.
 7. Aprotective gas generating heating system for asphalt tanks comprising,a. the structure in accordance with claim 1 in which, b. the saidinsulation means are a jacket through which the said stack extends, thejacket extending from approximately the level of the said heatgenerating means the top of the first said tank, c. the jacket beingclosed at the bottom against the intrusion of asphalt and open to thecirculation of air at the top of the first said tank, the jacket beingin spaced relationship to the stack.
 8. A protective gas generatingheating system for asphalt tanks comprising, a. the structure inaccordance with claim 1 in which, b. the heat generating means producesan exhaust gas which is predominantly carbon dioxide.
 9. A protectivegas generating heating system for asphalt tanks comprising, a. thestructure in accordance with claim 1 and, b. gas pressure regulatormeans operatively connected to the conduit means intermediate the saidaccumulator tank and the first said tank, c. the said heat generatingmeans being positioned proximal to the bottom of the first said tank andproducing an exhaust gas which is predominantly carbon dioxide.
 10. Aprotective gas generating heating system for asphalt tanks comprising,a. the structure in accordance with claim 9, in which b. the saidinsulation means are a jacket through which the said stack extends, thejacket extending from approximately the level of the said heatgenerating means to the top of the first said tank, c. the jacket beingclosed at the bottom against the intrusion of asphalt and open to thecirculation of air at the top of the first said tank, the jacket beingin spaced relationship to the stack.